Giardia and Cryptosporidium on dairy farms and the role these farms may play in contaminating water sources in Prince Edward Island, Canada.

BACKGROUND: Cattle represent a reservoir for Giardia and Cryptosporidium and may contaminate water sources. OBJECTIVES: To determine the distribution of Cryptosporidium and Giardia on dairy farms and in water bodies near the farms. FARMS AND WATER SOURCES: Twenty dairy farms and 20 wells and 13 surface water samples associated with dairy farms. METHODS: Proportions of samples positive for Cryptosporidium or Giardia were determined by a direct immunofluorescence assay. Fecal and water samples were taken at different times. RESULTS: Thirty-two (95% CI: 29-35%) and 14% (95% CI: 12-17%) of fecal samples, and 100 (95% CI: 96-100) and 55% (95% CI: 32-77%) of herds, were positive for Giardia and Cryptosporidium, respectively. Giardia duodenalis assemblage E was detected in high proportions (90%) of fecal samples. Cryptosporidium bovis predominated (51%) in all cattle. C. andersoni predominated in adult cattle (53%), whereas the predominant species in animals < 2 months and 2-6 months was C. bovis, respectively. Only calves < 2 months of age were positive for C. parvum. In 46% (95% CI: 19-75%) and 85% (95% CI: 55-98%) of surface water, concentrations of Giardia cysts and Cryptosporidium oocysts were higher in downstream, than in upstream, locations of farms, whereas only 1 groundwater sample was positive for Cryptosporidium. CONCLUSIONS: This sample of dairy cattle was predominantly infected with nonzoonotic species and genotypes of Cryptosporidium, Giardia, or both. More studies are needed to determine if the presence of Giardia or Cryptosporidium in surface water was associated with shedding in animals from nearby farms.

Molecular epidemiology of Cryptosporidium and Giardia in humans on Prince Edward Island, Canada: evidence of zoonotic transmission from cattle.

To determine the zoonotic potential of Cryptosporidium and Giardia in Prince Edward Island (PEI), Canada, 658 human faecal specimens were screened that were submitted to the Queen Elizabeth Hospital diagnostic laboratory. Overall, 143 (22%) samples were Cryptosporidium positive, while three (0.5%) were positive for Giardia. Successful genotyping of 25 Cryptosporidium isolates by sequence analysis of the HSP70 gene revealed that 28 and 72% were C. hominis and C. parvum, respectively. Cryptosporidium isolates from humans and previously genotyped C. parvum from beef cattle were subtyped by sequence analysis of the GP60 gene. Subtyping identified three subtypes belonging to the family IIa. All three subtypes IIaA16G2RI (55%), IIaA16G3RI (22%) and IIaA15G2RI (22%) were found in the animal isolates, while two of the subtypes found in the animals, IIaA16G2RI (80%) and IIaA15G2RI (20%), were also identified in the human isolates. Cryptosporidium infection in humans peaked in April-June. Molecular epidemiological analysis of the human data showed a C. parvum peak in the spring and a relatively smaller peak for C. hominis in July-September. The majority (57%) of human Cryptosporidium isolates were found in children between 5 and 10 years of age. All three Giardia isolates were identified as G. duodenalis assemblage A. The overall Cryptosporidium prevalence in our human samples was high relative to other studies, but because the samples were submitted to a hospital diagnostic laboratory, the results may not be representative of the general population. Further, the presence of the same zoonotic C. parvum subtypes in cattle and human isolates implies that transmission is largely zoonotic and cattle may be a source of sporadic human infections on PEI. The presence of Giardia in people on PEI is rare, and the assemblage A found in humans might originate from humans, livestock or other domestic or wild animals.

Combined effect of nisin and moderate heat on destruction of Listeria monocytogenes in cold-pack lobster meat.

The combined effect of nisin and moderate heat to increase the killing of Listeria monocytogenes in cans of "cold-pack" lobster was investigated. Adding nisin at a level of 25 mg/kg of can contents to the brine surrounding the lobster, in combination with a heat process giving internal can temperatures of 60 degrees C for 5 min and 65 degrees C for 2 min, resulted in decimal reductions of inoculated L. monocytogenes of 3 to 5 logs, whereas heat or nisin alone resulted in decimal reductions of 1 to 3 logs. Such a reduced heat process to that currently commercially used (65.5 degrees C for 13 to 18 min, depending on the can size) results in significant reduction in drained weight loss, thus allowing considerable cost savings to the lobster-processing industry.

Evaluation of different antimicrobial agents used as selective supplements for isolation and recovery of Yersinia enterocolitica.

Seventeen antimicrobial agents were evaluated separately or in combination for their efficiency as selective supplements in a broth medium against six different serotypes of Yersinia enterocolitica and 20 selected strains of different Gram-negative bacteria. Irgasan (DP300, 5-chloro-2-(2,4- dichlorophenoxy) phenol) at a concentration of 4 micrograms ml-1 inhibited the growth of most Gram-negative bacteria with the exceptions of Aeromonas hydrophila, Morganella morganii, Pseudomonas aeruginosa and Serratia liquefaciens. Other antimicrobial agents incorporated in the growth medium, separately or in combination with Irgasan, either inhibited some strains of Y. enterocolitica or did not inhibit the growth of Irgasan-resistant Gram-negative bacteria.

Evaluation of the ability of primary selective enrichment to resuscitate heat-injured and freeze-injured Listeria monocytogenes cells.

Resuscitation rates of injured Listeria monocytogenes on conventional selective Listeria enrichment broth and nonselective Trypticase soy broth containing 0.6% yeast extract were compared. Cells were heated to 60 degrees C for 5 min or frozen at -20 degrees C for 7 days. Inoculation of Trypticase soy broth-yeast extract with the stressed cells resulted in growth that was superior to that in Listeria enrichment broth. Injured cells were fully recovered at 6 to 8 h.